GB1369939A - Transponder for telemetering system - Google Patents

Abstract

1369939 Telemetry systems INTERNATIONAL STANDARD ELECTRIC CORP Dec 1972 [16 Dec 1971] 57758/72 Headings G4D D6M3 D6Y D6C1 and D6C2 [Also in Division H4] A telemetry system for reading one or more remote meters A, B, C comprises a respective memory 14 and a shift register 16 for storing the reading of each meter, a control circuit 35 responsive to a signal supplied from a telephone network interface unit 22 via a receiver 30 and a telephone line unit 24 for reading out the stored data, and an encoder 40 for converting the data into tone signals which are transmitted to a central data processor 20. Each meter, which may be a gas, water or electricity meter generates pulses by means of a respective switch Al, B1, Cl closed by an associated reed switch as the meter reading changes, the pulses being shaped in a buffer circuit 12 and counted by counters in the memory 14. Each memory supplies a binary coded decimal output to the respective shift register 16. When the meter readings are to be transferred to the processor 20, the unit 22 sends a 697 Hz signal to the receiver 30 via the unit 24. The frequency and duration of the signal are checked by the circuits 30, 35 and if satisfactory, the circuit 35 supplies a signal to a power supply circuit 45 to cause a battery to be connected to the shift registers and to a multivibrator in the encoder 40. The multi-vibrator supplies clockpulses on a line 235 to the circuit 35. The clockpulses are fed to the shift registers via a line 228 to enable the serial read-out of sixteen data bits from each register. The encoder converts the data into a form in which each bit is represented by one of two frequencies, the data being transmitted over a telephone line 26 to the processor 20 via a gate 224 opened by the 697 Hz signal. After the transmission of the total 48 bits of data, a signal from a clockpulse counter in the circuit 35 closes the gate 224 and switches off the power supply to the encoder and shift registers. If a telephone subscriber whose meters are being read lifts the receiver, the data transmission is stopped and since all the 48 data bits have not been received by the processor, the partial data transmitted is erased. The battery in the supply 45 is charged from a recitified 12 volt A.C. supply and if prolonged failure of the A.C. supply causes excessive discharge of the battery the power supplied to the receiver 30 on a line 350 is switched off to prevent operation of the system.